Magnetic recording system with medium having antiferromagnetic-to- ferromagnetic transition layer exchange-coupled to recording layer

Abstract

A magnetic recording disk drive has a bilayer recording medium of a high-anisotropy recording layer and an exchange-coupled antiferromagnetic-to-ferromagnetic (AF-F) transition layer. The transition layer has an AF-F transition temperature (T AF-F ) that decreases relatively rapidly with increasing applied magnetic field. Thus the transition layer has a transition field H AF-F (T), which is the applied magnetic field required to transition the material from antiferromagnetic to ferromagnetic at temperature T without the need to heat the layer. At ambient temperature and in the absence of H W , the transition layer is antiferromagnetic and the switching field H 0 of the bilayer is just the H 0 of the high-anisotropy recording layer, which is typically much higher than H W . In the presence of the write field H W the transition layer transitions from antiferromagnetic to ferromagnetic so that data can be written to the recording by the mere application of the write field H W without the need to heat the transition layer or recording layer. The transition layer may be formed of Fe(RhM), where M is an element selected from V, Mn, Au and Ni.

1 . A magnetic recording system comprising:
 a write head for generating a magnetic write field (H W ); and   a magnetic recording medium comprising
 a substrate; 
 an antiferromagnetic-to-ferromagnetic (AF-F) transition layer on the substrate and having a transition field (H AF-F ) less than H W ; and 
 a ferromagnetic recording layer in contact with the transition layer, the transition layer and recording layer being exchange-coupled ferromagnetically when the transition layer is in its ferromagnetic state after exposure to H W . 
   
   
   
       2 . The system of  claim 1  wherein the transition layer comprises an alloy comprising Fe and Rh. 
   
   
       3 . The system of  claim 2  wherein the transition layer comprises Fe(RhM), where M is an element selected from the group consisting of Pd, V, Mn, Au, and Ni. 
   
   
       4 . The system of  claim 3  wherein the Fe(RhM) is Fe x (Rh 100-y M y ) 100-x , where y is between about 0 and 15, and x is between about 40 and 55. 
   
   
       5 . The system of  claim 1  wherein the operating temperature range of the system is between T L  and T H , and wherein the transition layer has an AF-F transition temperature T AF-F  greater than T H  in the absence of H W  and a T AF-F  less than T L  in the presence of H W . 
   
   
       6 . The system of  claim 1  wherein the transition layer is located between the substrate and the recording layer. 
   
   
       7 . The system of  claim 1  wherein the recording layer has horizontal magnetic anisotropy. 
   
   
       8 . The system of  claim 1  wherein the recording layer has perpendicular magnetic anisotropy. 
   
   
       9 . The system of  claim 1  wherein the recording layer comprises a chemically-ordered alloy selected from alloys of FePt, CoPt, FePd, CoPd, CoPt 3  and CoPd 3 . 
   
   
       10 . The system of  claim 1  wherein the recording layer comprises a chemically-ordered L 1   0  phase alloy selected from FePt—X and CoPt—X, where the element X is selected from the group consisting of Ni, Au, Cu, Pd and Ag. 
   
   
       11 . The system of  claim 1  wherein the recording layer comprises a multilayer selected from the group consisting of Co/Pt, Co/Pd, Fe/Pt and Fe/Pd multilayers. 
   
   
       12 . The system of  claim 1  further comprising a protective overcoat over the recording layer. 
   
   
       13 . A magnetic recording disk drive having an operating temperature range between T L  and T H  and comprising:
 a write head for generating a magnetic write field (H W ); and   a magnetic recording medium comprising
 a substrate; 
 an antiferromagnetic-to-ferromagnetic (AF-F) transition layer on the substrate and having a transition field (H AF-F ) less than H W , the transition layer having a transition temperature (T AF-F ) greater than T H  in the absence of H W  and a T AF-F  less than T L  in the presence of H W ; and 
 a ferromagnetic recording layer in contact with the transition layer, the transition layer and recording layer being exchange-coupled ferromagnetically when the transition layer is in its ferromagnetic state after exposure to H W . 
   
   
   
       14 . The disk drive of  claim 13  wherein the transition layer comprises Fe(RhM), where M is an element selected from the group consisting of Pd, V, Mn, Au, and Ni. 
   
   
       15 . The disk drive of  claim 14  wherein the Fe(RhM) is Fe x (Rh 100-y M y ) 100-x , where y is between about 0 and 15, and x is between about 40 and 55. 
   
   
       16 . The disk drive of  claim 13  wherein the transition layer is located between the substrate and the recording layer. 
   
   
       17 . The disk drive of  claim 13  wherein the recording layer has horizontal magnetic anisotropy. 
   
   
       18 . The disk drive of  claim 13  wherein the recording layer has perpendicular magnetic anisotropy. 
   
   
       19 . The disk drive of  claim 13  wherein the recording layer comprises a chemically-ordered alloy selected from alloys of FePt, CoPt, FePd, CoPd, CoPt 3  and CoPd 3 . 
   
   
       20 . The disk drive of  claim 13  wherein the recording layer comprises a chemically-ordered L 1   0  phase alloy selected from FePt—X and CoPt—X, where the element X is selected from the group consisting of Ni, Au, Cu, Pd and Ag. 
   
   
       21 . The disk drive of  claim 13  wherein the recording layer comprises a multilayer selected from the group consisting of Co/Pt, Co/Pd, Fe/Pt and Fe/Pd multilayers. 
   
   
       22 . The disk drive of  claim 13  further comprising a protective overcoat over the recording layer.